Vehicles, such as trucks, are frequently used for transporting valuable cargo, such as electronics, computers and other goods that may easily be sold. Since the cargo often is transported over long distances, the trucks may be equipped with sleeping cabins, allowing the driver to park at the road-side and rest during the night, leaving the cargo essentially unattended. The problem of unattended valuable cargo in trucks is also present when trucks are left parked at fenced loading/unloading areas.
Unfortunately, theft of goods from such unattended trucks is a constantly increasing problem, resulting in great economical losses for companies and individuals using trucks for transporting goods. The extent of the problem has been a surprise to both the police and the freight business. However, this problem is not limited to trucks, but is also an issue for parked trailers, buses, railway-carriages and the like. Since the goods and valuables are left unattended there is unfortunately in many situations plenty of time for criminals to steal large amounts of valuable goods. Sometimes, the intruders simply drive off with entire trucks or trailers
Trucks and trailers are often more vulnerable to the above problem than other types of vehicles since they often are equipped with fabric covers which can either be easily opened by an intruder or—if locked—easily cut open with sharp objects. One obvious solution to this problem is to use hard cargo covers which, however, has the drawback that a thief, trying to gain access to the cargo, only needs to force the locks at the back or the side doors of the truck or trailer.
Different kinds of alarm systems may be used to make it more difficult for an intruder to gain access to a vehicle. Different methods for detecting an intrusion have been described in the art.
EP-A1-1 720 142 discloses a vehicle security monitor system, including motion detectors for detecting a motion of an object within security zones of the vehicle and cameras for generating video images of the security zones. When the camera is activated, the captured images are shown on an onboard display.
WO 03/105100 A1 discloses a vehicle security system in which laser beams or IR beams are directed along the sides of the vehicle in order to detect any unauthorized approach to the vehicle. An alert to a security company may be provided via remote notification.
WO 95/01890 discloses a vehicle security system providing IR intrusion detection within a detection zone surrounding a vehicle. An IR sensor detects a thermal energy flux reflected or radiated from a direction of interest and produces an electrical input having an input signal level associated with the flux. An electronic circuit compares the input signal level with a pre-selected trigger level and produces an alert signal if the input signal level becomes equal to or greater than the trigger signal level. The electronic circuit further includes an alarm, such as a visual indicator or an audible signal, for receiving the alert signal and for producing a warning effect detectable by an occupant within the vehicle.
These prior-art security systems has the drawback that they require a substantial amount of extra equipment and wiring to the vehicle and are cumbersome to install on trucks and caravans, especially if the vehicle has a trailer.